QTL analysis of chlorophyll content and chlorophyll fluorescence

QTL analysis of chlorophyll content and chlorophyll fluorescence

FOLIA POMERANAE UNIVERSITATIS TECHNOLOGIAE STETINENSIS
Folia Pomer. Univ. Technol. Stetin., Agric., Aliment., Pisc., Zootech. 2014, 312(31), 105–116
Katarzyna MOLIK, Edyta PAWŁOWSKA, Zuzanna KANTAREK,
Paweł MILCZARSKI1
QTL ANALYSIS OF CHLOROPHYLL CONTENT AND CHLOROPHYLL
FLUORESCENCE PARAMETER IN MAPPING POPULATION OF RYE
ANALIZA QTL ZAWARTOŚCI CHLOROFILU I PARAMETRU FLUORESCENCJI
CHLOROFILU W POPULACJI MAPUJĄCEJ ŻYTA
Department of Plant Genetics, Breeding and Biotechnology, West Pomeranian University
of Technology, Szczecin, Poland
Streszczenie. Zdefiniowano QTL dla zawartości chlorofilu (Chc) i maksymalnej fotochemicznej
aktywności PSII (Fv/Fm) żyta. Materiał do badań stanowiła populacja RIL mieszańca
międzyliniowego DS2 × RXL10, złożona z 70 osobników pokolenia F7. Otrzymane wyniki
poddano analizie statystycznej; stwierdzono istotne zróżnicowanie obu cech u form
rodzicielskich i osobników w populacji mapującej. Nie zaobserwowano istotnej statystycznie
korelacji pomiędzy Chc a Fv/Fm; obliczone współczynniki odziedziczalności w szerokim zakresie
(HB) wynosiły odpowiednio 56 i 53%. Przy LOD ≥ 2,0 wyznaczono 19 regionów QTL, w tym
9 dla zawartości chlorofilu i 10 dla całkowitej wydajności fotochemicznej PSII. Lokalizowały się
one głównie w dystalnych lub centromerowych obszarach chromosomów: 1R, 3R, 5R, 6R, 7R,
przy czym na chromosomach 1R, 5R i 6R znalazły się regiony wspólne dla QTL Fv/Fm1
i Fv/Fm5 (1R), Chc8 i Fv/Fm9 (5R) oraz Fv/Fm3 i Fv/Fm10 (6R). Otrzymane QTL dostarczają
wstępnej wiedzy o dziedzicznym podłożu zawartości chlorofilu w życie i maksymalnej
fotochemicznej aktywności PSII.
Key words: chlorophyll content, chlorophyll fluorescence, genetic mapping, rye, QTL.
Słowa kluczowe: fluorescencja chlorofilu, mapowanie genetyczne, QTL, zawartość chlorofilu, żyto.
INTRODUCTION
The development of technology generating a large amount of molecular markers in a short
time allowed for the acceleration of research aimed at identifying heritable basis of
quantitative traits determined by multiple genes. The first stage of the study on the
quantitative trait loci (QTL) mapping is the construction of a genetic map. On the map, one
can localize regions, with a high probability of the occurrence of a gene responsible for the
expression of a trait. Such studies are performed for the majority of crop species, including
rye. In terms of rye, the studies concern mainly morphological, yielding, physiological and
qualitative traits (Milczarski 2008; Börner et al. 2009; Masojć and Milczarski 2009; Miedaner
et al. 2012; Myśków et al. 2014).
Corresponding author – Adres do korespondencji: MSc Katarzyna Molik, Department of Plant
Genetics, Breeding and Biotechnology, West Pomeranian University of Technology, Szczecin,
Juliusza Słowackiego 17, 71-434 Szczecin, Poland, e-mail: [email protected]
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K. Molik et al.
Most of these studies comprise the analyses of the most important agronomic trait - yield
or its components. Photosynthetic efficiency constitutes the most important factor affecting
plant growth, biomass accumulation and thus grain yield to a significant extent. One of the
factors stimulating the intensity of photosynthetic process is synthesis of photosynthetic
pigments, mainly chlorophylls. Their total content in leaves, measured in appropriate and
under favorable conditions, can be used as a reliable marker of the efficiency of PSII
photosystem (Vijayalakshmi et al. 2010). One of the parameters of PSII efficiency is a
parameter of induced chlorophyll fluorescence – Fv/Fm,, which is defined as the ratio of the
maximum quantum efficiency of PSII photochemistry. It only provides the information on the
maximum potential of photosynthetic apparatus, at which light energy absorbed by PSII is
used for the total reduction of primary electron acceptor QA, and not for the real quantum
productivity of PSII. The objective of this study was to identify QTLs, which control the
chlorophyll content and the maximum PSII photochemical productivity on the genetic map of
recombinant rye inbred lines (RIL) of DS2 × RXL10 hybrid cross.
MATERIAL AND METHODS
Plant material consisted of parental inbred lines: DS2 and RXL10 as well as 70 hybrids of
F7 (S6) generation (RIL population), derived by SSD (Single Seed Descent) method by
Milczarski (2010). From plants, in the earring stage, growing on experimental microplots in
the Agricultural Academy in Szczecin (nowadays West Pomeranian University of Technology
in Szczecin) between 2004–2005, three flag leaves from three different plants in two
replications in each year were collected. On the cut leaves, the kinetics of fluorescence was
measured with the use of PEA fluorometer (Hansatech, Kings Lynn, UK). The measurement
was performed in the middle part of the leaf, after prior shading with a clip for a period of
20 minutes. The measurement of chlorophyll fluorescence was initiated from the illumination
of previously shaded sample by the light of low intensity (3000 µmol · m–2 · s–1 during 1s) in order
to open the energy traps. The first registered parameter was the primary fluorescence (F0).
Then, the samples were illuminated by a saturating flash of light, which allowed for the
registration of maximum fluorescence (FM). This enabled determination of the maximum
quantum efficiency of PSII from the equation: FV/FM = (FM–F0)/FM. Among the obtained
parameters, for further analyses maximum photochemical productivity of PSII (Fv/Fm) was
selected. On the same leaves, the chlorophyll content (Chc) was determined using SPAD
502 chlorophyll meter (Minolta, Japan) according to the instruction. The obtained values in
SPAD units are contractual and do not represent the absolute chlorophyll content, but are
proportional to its amount.
The results of the measurements were subjected to statistical analysis with the use of
Statistica 10.0 (StatSoft, Inc. 2010) and parameters: mean value of a trait ( x ), minimum
(min.) and maximum (max.) values, standard deviation (SD) and coefficient of variation (CV)
were calculated. Distribution of the traits was evaluated by testing the significance of the
deviation using the Kolmogorov-Smirnov test. The mean values of the traits tested at the turn
of years in all subjects, were used to determine linear correlation coefficient. Data obtained
from replicates in years was used for the evaluation of genotype-environment interactions.
QTL analysis of chlorophyll content
107
Based on the analysis of variance, broad sense heritability (HB) was calculated according to
the formula proposed by Holland et al (2003). Significance of the differences between the
parental lines was tested by Student's t test.
In this study, genetic maps of DS2 × RXL10 hybrid published by Milczarski et al. (2011),
were used. These maps consisted mainly of DArT markers with the addition of a few markers
of a different type: SCAR, SSR, RAPD. The number of markers on the maps was reduced by
removing the majority of redundant ones. These maps were used to identify QTLs by using
WinQTL Cartographer 2.5 program (Wang et al. 2011). QTL mapping was performed using
composite interval mapping (CIM). It allows to establish the linkage between QTL and
markers of the genetic map by identification of the chromosome region with the maximum
probability of gene location determining a given trait. QTL position is identified in the region,
for which the LOD (logarithm of odds) curve exceeds the critical level established in our
study at LOD = 3.0. In addition, QTLs identified within LOD range of 2.0–3.0 were also
considered, treating them as less certain loci. The parameters characterizing a particular
QTL are: LOD critical value, position of the marker most strongly associated with a QTL
(maximum of LOD curve), QTL interval, determination coefficient of a trait (R2) and the
additive effect of parental allele.
RESULTS
The basic assumption to identify QTLs using CIM method is the diversity of parental
components and the trait distribution in the mapping population close to a normal distribution.
The analysis of variance of investigated traits in the parental lines revealed that parents differ
significantly in case of both Fv/Fm and Chc as well (Table 1).
Table 1. Mean values of two-year measurements of chlorophyll content (Chc) in SPAD units and
maximal photochemical efficiency of PSII (Fv/Fm) (± standard deviation), for parental lines
Tabela 1. Średnie zawartości chlorofilu (Chc), w jednostkach SPAD, i maksymalnej fotochemicznej
wydajności PSII (Fv/Fm) (± odchylenie standardowe) dla linii rodzicielskich w okresie dwóch lat
prowadzenia doświadczenia
Trait
Cecha
Mean trait value for parental lines
Wartość średnia cechy u rodziców (± SD)
DS2
RXL10
p
Chc (SPAD)
43.067 ± 3.447
50.467 ± 3.489
0.023*
Fv/Fm
0.827 ± 0.002
0.809 ± 0.009
0.009*
p – probability of t Student test statistics – prawdopodobieństwo statystyki t testu Studenta.
* Significant differences of traits between parental lines with p ≤ 0.05 – Istotne różnice cech pomiędzy liniami
rodzicielskimi dla p ≤ 0,05.
In the case of Fv/Fm evaluated in both years, the coefficient of variation of the individuals in
RIL population was very low and was estimated at a maximum of 3.3%. The reason for such
low CV values was the low diversity of the trait (Table 2). Both traits had a normal distribution
in a mapping population with the exception of Fv/Fm evaluated in 2005, where statistically
significant deviation from the assumed trait distribution was reported by flattening and right
shift of the curve (Table 2).
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K. Molik et al.
Table 2. Mean values of chlorophyll content (SPAD) and maximal photochemical efficiency of PSII for
RIL population DS2 × RXL10 (± standard deviation), minimum (min.), maximum (max.), coefficient
of variation (CV), Kolmogorov-Smirnov (K-S) test values and parameters of trait distribution –
skewness and kurtosis
Tabela 2. Średnie zawartości chlorofilu (SPAD) i maksymalnej fotochemicznej wydajności PSII dla
populacji RIL DS2 × RXL10 (± odchylenie standardowe), minimum (min.) maksimum (max.),
współczynnik zmienności (CV), wartości testu Kołmogorowa-Smirnowa oraz parametry rozkładu
cechy – skośność i kurtoza
Trait
Cecha
Chc
(SPAD)
Year
Rok
DS2 × RXL10 RIL population
Populacja RIL DS2 × RXL10
CV
K-S test
skewnesss
max.
[%]
test K-S
skośność
mean
średnia (± SD)
min.
kurtosis
kurtoza
2004
45.045 ± 6.412
30.20
61.00
14.23
0.060
–0.033
0.063
2005
41.679 ± 4.287
32.24
53.48
10.29
0.073
–0.369
0.554
2004
0.821 ± 0.009
00.80
00.84
01.15
0.076
–0.417
0.496
2005
0.808 ± 0.027
00.72
00.85
03.30
0.123*
–1.247
1.419
Fv/Fm
* Significant distortion of normal distribution with p ≤ 0.05 – Istotne odchylenie od rozkładu normalnego dla p ≤ 0,05.
The variance (mean squares) of investigated traits was significant for years, genotypes
and interactions, except for Chc (Table 3). For this trait no significant interaction between
years and genotypes was observed. Using the components of the analysis of variance, broad
sense heritabilities were estimated (HB). It was found, that the heritability of Fv/Fm, despite
a little variation within the population, was high and was estimated at 0.53. A slightly higher
rate of this parameter was obtained for Chc. The estimated level of phenotypic correlations
between Fv/Fm and Chc was not statistically significant (Table 4). However, one reported the
correlation between the same trait measured in subsequent years.
Table 3. Variance analysis of chlorophyll content (SPAD) and maximal photochemical efficiency
of PSII for variables: year, genotype, interaction year × genotype and broad-sense heritability HB
Tabela 3. Analiza wariancji zawartości chlorofilu (SPAD) i maksymalnej fotochemicznej wydajności
PSII dla roku, genotypu, interakcji rok × genotyp oraz współczynnik odziedziczalności HB
Source of variation
Źródło zmienności
Year
Rok
Genotype
Genotyp
Year × Genotype
Rok × Genotyp
Error
Błąd
HB
Degrees of freedom
Stopnie swobody
Trait
Cecha
Chc
mean squares
średnie kwadraty
p
Fv/Fm
mean squares
średnie kwadraty
p
001
o o93.651*
0.038
0.008*
0.000
069
4820.608*
0.000
0.050*
0.000
069
o658.314*
0.990
0.025*
0.000
140
2974.947*
–
0.011*
–
0.56
0.53
* Significance of variance with p ≤ 0.05 – Istotność wariancji na poziomie p ≤ 0,05.
Mean squares, number of degrees of freedom and probability of F statistics (p) were given – Podano średnie
kwadraty, liczbę stopni swobody i prawdopodobieństwo statystyki F (p).
QTL analysis of chlorophyll content
109
Table 4. Correlation matrix mean values between chlorophyll content and maximal photochemical
efficiency of PSII for two-year measurements: 2004 (Chc2004, Fv/Fm2004) and 2005 (Chc2005,
Fv/Fm2005)
Tabela 4. Macierz korelacji średnich zawartości chlorofilu i maksymalnej fotochemicznej aktywności
PSII w populacji RIL, wraz z pomiarami z 2004 r. (Chc2004, Fv/Fm2004) i 2005 r. (Chc2005,
Fv/Fm2005)
Cecha
Trait
Fv/Fm2004
Fv/Fm2004
Chc2004
Fv/Fm2005
Chc2005
–
Chc2004
–0.011
–
Fv/Fm2005
0.490
0.088
–
Chc2005
0.169
0.649
0.138
–
n – sample size – wielkość próby.
Statistically important correlations between phenotypic traits were marked grey, for n = 70 – Kolorem szarym
zaznaczono statystycznie istotne korelacje pomiędzy cechami fenotypowymi, dla n = 70.
Averaged measurements of the traits were introduced to WinQTL Cartographer program
to identify QTL regions determining Fv/Fm and Chc. A total of 19 QTLs were identified,
including the most for Fv/Fm in 2005, and the least for Chc in 2005 and Fv/Fm in 2004, namely
9,3 and 3 respectively (Table 5). Identified QTLs were mapped on 1R, 3R, 5R, 6R and 7R
chromosomes of rye (Fig. 1, Table 5). 14 of the identified QTLs showed the confidence of
identification measured by the LOD test exceeding the critical value of 3.0. Among these loci,
Fv/Fm9 was characterized by the highest level of LOD, exceeding 52. Distribution of QTLs on
chromosomes was not uniform. They were mostly located in the distal regions of the
chromosomes (1R, 5R, 6R and 7R) or near the centromere (3R and 6R). Three regions
common for the QTLs were detected: one for different traits (Chc8, Fv/Fm9 on 5RL) and two
for the same trait evaluated in different years (Fv/Fm1, Fv/Fm5 on 1RS and Fv/Fm3, Fv/Fm10
on 6RS). The remaining QTLs occurred individually.
DISCUSSION
The most important agronomic trait of crops, including rye, is yield. Among a number of
traits affecting the yield of rye grains, a huge importance is attributed to the morphological
features such as the size and the area of the flag leaf as well as the successive leaves, blade
and physiological features such as chlorophyll content and photosynthetic activity (Xue et al.
2008). The measurement of the photosynthetic activity can be performed using fluorescence
analysis of chlorophyll. It is a non-invasive and non-destructive method for plants, and at the
same time it can be conducted in field research (Hur et al. 2009; Kalaji and Łoboda 2009).
The results of these measurements inform about the progress of biophysical phenomena and
biochemical processes occurring within photosystem II (PSII). Moreover, they are designed
to assess the impact of external factors, including stress, on photosynthetic efficiency
(Kalaji and Łoboda 2009). The intensity of photosynthetic process, including the efficiency
of photosystem II is stimulated by the synthesis of photosynthetic pigments, especially
chlorophyll (Vijayalakshmi et al. 2010). Increase in the concentration of chlorophyll in
the plant can be an effective way to improve the production of biomass, and thus the yield
(Wang et al. 2008).
Table 5. Characteristic of QTLs controlling chlorophyll content and maximal photochemical efficiency of PSII for RIL mapping population DS2 × RXL10
Tabela 5. Charakterystyka QTL kontrolujących zawartość chlorofilu oraz całkowitą fotochemiczną aktywność PSII dla populacji mapującej RIL DS2 × RXL10
Trait
Cecha
Year
Rok
Chc
2004
2005
Fv/Fm
2004
2005
QTL symbol
Symbol QTL
Chromosome
Chromosom
Chc1
1R
QTL peak position in cM
(QTL interval)
Pozycja piku QTL w cM
(przedział QTL)
200.30 (192.5–203.3)
Chc2
5R
Chc3*
2
LOD
XrPt401180 (3.0)
4.69
2.45
27.03
125.60 (125.3–126.6)
XrPt508209 (0.0)
4.02
–1.73
13.70
6R
66.1
XrPt400119 (0.0)
2.09
–1.18
05.84
Chc4*
6R
83.9 (82.9–84.0)
XrPt505336 (0.1)
2.18
1.33
08.13
Chc5*
6R
228.7 (228.7–229.7)
XrPt505447 (0.0)
2.77
1.39
08.91
Chc6
7R
259.1 (257.5–258.1)
XrPt389927 (0.0)
6.23
–2.27
23.81
Chc7
3R
94.8 (92.5–94.8)
XrPt66766 (1.0)
3.46
7.64
21.28
Chc8
5R
171.3 (170.3–173.3)
XrPt399270 (9.9)
17.78
19.16
46.15
Chc9
6R
215.3 (214.7–215.3)
XrPt400168 (0.0)
4.75
–7.29
19.78
Fv/Fm1
1R
25.3 (25.2–25.3)
XrPt506276 (0.0)
4.12
0.12
15.65
Fv/Fm2
3R
121.5
XrPt410986 (0.0)
3.32
–0.11
12.93
Fv/Fm3
6R
7.9 (7.9–8.0)
XrPt410992 (0.1)
6.41
–0.17
27.39
Fv/Fm4
1R
14.6 (8.6–14.7)
XrPt400359 (0.1)
2.24
–0.11
10.40
Fv/Fm5
1R
25.3 (25.2–25.3)
XrPt506276 (0.0)
5.05
0.13
17.77
Fv/Fm6
3R
62.4 (62.4–64.4)
XrPt399942 (0.0)
3.43
–0.09
08.98
Fv/Fm7
3R
85.0 (85.0–85.2)
XrPt346908 (0.2)
3.11
0.12
15.60
Fv/Fm8*
5R
22.9 (22.8–24.9)
XrPt411232 (0.0)
2.56
–0.09
08.48
Fv/Fm9
5R
172.3 (164.3–175.3)
XrPt399270 (8.9)
52.82
0.40
44.41
Fv/Fm10
6R
8.0 (7.9–8.0)
XrPt410992 (0.0)
4.84
–0.13
17.49
* QTLs with LOD score = 2.00–3.00 – QTL o niższej wiarygodności, z wartością LOD = 2,00–3,00.
Additive effect
Efekt addytywny
R
[%]
Nearest marker
Najbliższy marker (cM)
Fig. 1. Localization of QTLs for chlorophyll content (Chc) and maximal photochemical efficiency of PSII (Fv/Fm) for RIL population, for two-year measurements
(2004, 2005). Nearest markers for QTLs were marked
Ryc. 1. Lokalizacja QTL zawartości chlorofilu (Chc) i całkowitej aktywności fotochemicznej PSII (Fv/Fm) w populacji RIL dla pomiarów wykonanych w latach
2004 i 2005. Zaznaczone markery zlokalizowano najbliżej obszaru QTL
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K. Molik et al.
Quantitative traits are determined both by environmental and genetic factors.
Understanding of the genetic basis of a particular quantitative trait is possible by using
genetic maps and tools for the identification of QTL. The high-density map used in this study
consists of 1391 markers of DS2 x RXL10 population (Milczarski et al. 2011). However, for
the analysis of QTL, a smaller number of individuals was available at the time of
measurement. It should be emphasized, that such number of mapping population is
insufficient for the precise localization of QTLs, and the obtained results should be treated as
preliminary recognition of hereditary basis of investigated traits. In this paper an attempt was
made to determine the probable number of QTLs determining maximum photochemical
productivity of PSII (Fv/Fm) and chlorophyll content (Chc). Similarly as in this study, a number
of authors (Li et al. 2006; Zhang et al. 2010; Kumar et al. 2012; Czyczyło-Mysza et al. 2013)
have not confirmed statistically significant correlation between the content of chlorophyll and
Fv/Fm in plants remaining in physiological condition. This situation changes dramatically when
the plants are subjected to e.g. prolonged drought-stress conditions (Zhang et al. 2010;
Kumar et al. 2012). It suggests a high sensitivity of the analyzed traits to external factors.
The Fv/Fm parameter selected for mapping is one of many possible to obtain from chlorophyll
fluorescence analysis. In the literature, this parameter as well as its components have been
widely used in the studies of QTL mapping of chlorophyll fluorescence under both, optimal
plant growth (Yang et al. 2007; Guo et al. 2008; Liang et al. 2010; Yin et al. 2010; Zhang
et al. 2010; Czyczyło-Mysza et al. 2013), as well as drought-stress conditions (Yang et al. 2007;
Kumar et al. 2010), or cold-stress conditions (Fracheboud et al. 2002; Jompuk et al. 2005;
Guo et al. 2008).
In the majority of the above-mentioned studies, authors used chlorophyll fluorescence
parameters to investigate the genetic basis of photosynthesis, and to compare the effect of
stress on different genotypes. Despite the small variation of Fv/Fm parameter and CV in the
range of 1.1–3.3%, in the course of this study 10 QTLs were identified, localized on 1R, 3R,
5R and 6R chromosomes. Four of them co-localized in two regions, Fv/Fm1 and Fv/Fm5 on the
short arm of 1R chromosome, and Fv/Fm3 and Fv/Fm10 on 6RS. After elimination of QTLs
which repeated their position in the same region, the number of QTLs for the Fv/Fm
parameter was 8, while Fv/Fm4 and Fv/Fm8 loci were mapped below the accepted threshold of
LOD equal to 3.0. The number of identified QTLs for Fv/Fm, in the studies conducted by other
authors, investigating especially wheat, was different and was estimated between three
(Liang et al. 2010; Zhang et al. 2010) to nine (Czyczyło-Mysza et al. 2013).
In terms of Fv/Fm9 QTL very high values of both, LOD test and R2 were obtained. The
presence of a gene essential for the PSII functioning in the interval mapping could be the
reason for such high values of the parameters describing QTL. Unfortunately, the closest
marker is located at a distance of approximately 9 cM, which prevents from verification of
such thesis. Chlorophyll content expressed in SPAD units was conditioned by the presence
of 9 QTLs, localized on 1R, 3R, 5R, 6R and 7R chromosomes. No co-localization of QTLs
detected in different growing seasons was observed, although some loci were located on the
same chromosome arms (6RS and 6RL) in close proximity. A more detailed analysis of QTL
additive effects of Chc from 6R chromosome showed that the indication of the activity of DS2
allele line for loci located near each other are different, which indicates dissimilarity
of detected QTLs.
QTL analysis of chlorophyll content
113
Milczarski and Masojć (2002) analyzing QTLs for Chc in the mapping population of the
same hybrid but obtained by sibling mating (F5 sib), identified 4 loci on 1RS, 3RS (C), 4RL
and 5RL chromosomes. Comparing our results with the results of their study, it was found
that the approximate common locations refer to QTLs identified on 3R and 5R chromosomes.
The highest values of the parameters describing the QTLs were reported for Chc8 localized
in the distal segment of 5R chromosome. Although there was no correlation between Chc
and Fv/Fm, Fv/Fm9 was also mapped in this region. For both QTLs, the values of parameters
describing QTLs seem to be overestimated and should be treated with caution. Similarly as
for Fv/Fm9, the distance of the most associated marker with the QTL is estimated at more
than 9 cM and no data on the function of this marker is available. Nevertheless, it is an
extremely important QTL region. In this area, a gene encoding recessive dwarfism in RXL10
line was localized. From studies conducted by Milczarski (2010), it can be concluded, that
this gene exhibits pleiotropy towards a number of traits. In this area QTLs for: spike length,
number of spikelets per spike, number of grains per spike, weight of grains per ear, weight of
1000 seeds and grain yield of plant were also identified. The analysis of the additive effect of
allele from DS2 line for both QTLs indicates, that the donor of favorable alleles which
increases the probability of both traits is DS2 line, although RXL10 line is characterized by
a higher content of chlorophyll in leaves. The presented distribution of QTLs on rye
chromosomes ensures complex and polygenic control of two important traits for the
functioning of the photosynthetic apparatus: chlorophyll content (Chc) and maximum
photochemical productivity of PSII (Fv/Fm).
CONCLUSIONS
The study allowed for the preliminary identification of 9 and 10 QTLs (including 2 QTLs
co-localizing on 1R and 6R) for the chlorophyll content and the maximum photochemical
productivity of PSII, respectively. Determination of the location of the QTLs determining Fv/Fm
has been the first such analyses for rye. Detected QTLs broaden the knowledge on rye
genome and provide new data useful for comparative analyses.
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Abstract. The objective of the study was to identify QTLs for the chlorophyll content (Chc) and
the maximum photochemical activity of PSII (Fv/Fm) in rye. RIL population of DS2 × RXL10
hybrid cross consisting of 70 individuals of F7 generation constituted as experimental material.
The obtained results were subjected to statistical analysis, and significant differences in the
diversity of both traits in parental phenotypes and individuals of mapping population, were
shown. No statistically significant correlation between Chc and Fv/Fm was observed, and
calculated broad sense heritabilities (HB) were estimated at 56 and 53% respectively. With LOD
score ≥ 2.0, 19 QTL regions were established, including 9 for the content of chlorophyll and 10
for a total photochemical efficiency of PSII. They were mainly localized in the distal or
centromeric regions of 1R, 3R, 5R, 6R, 7R chromosomes. On 1R, 5R and 6R common regions
for QTLs were found: Fv/Fm1 and Fv/Fm5 (1R), Chc8 and Fv/Fm9 (5R) as well as Fv/Fm3 and
Fv/Fm10 (6R). The resulting QTLs provide preliminary knowledge on hereditary basis of
chlorophyll content and maximum photochemical activity of PSII in rye.